The present invention relates to a leaf spring assembly for wheel suspensions, and more particularly to a leaf spring assembly of the type which comprises a longitudinal leaf spring made of fiber reinforced plastics, a pair of retainer plates attached to opposite surfaces of the leaf spring, and a pair of fastening U-bolts and nuts for clamping the retainer plates to the leaf spring and mounting the same on an axle housing.
In such a conventional leaf spring assembly as described above, it is required to facilitate positioning of the leaf spring at its center during mounting process of the leaf spring assembly. For such requirement, the central portion of the leaf spring is protruded or indented at its opposite faces, while the retainer plates are respectively indented or protruded to be coupled with the protruded or indented portions of the leaf spring. In FIG. 9(a) there is illustrated such a conventional leaf spring assembly in which a longitudinal leaf spring 1 of fiber reinforced plastics is provided at its central portion with a pair of upper and lower protrusions 2a and 2b, while a pair of upper and lower retainer plates 3 and 4 are respectively formed with protruded portions 3a and 4a coupled with the protrusions 2a and 2b of leaf spring 1. Thus, the leaf spring 1 is accurately positioned and retained in place by means of the retainer plates 3 and 4 coupled thereto. It has, however, been observed that as is illustrated in FIG. 9(b), there occur cracks 2c along with reinforcement fibrous sheet-like materials in the upper protrusion 2a of leaf spring 1, resulting in decrease of durability of the leaf spring 1. In FIG. 10(a) there is illustrated another conventional leaf spring assembly in which a longitudinal leaf spring 5 of fiber reinforced plastics is protruded upwardly at its central portion to form an upper protrusion 6a and a lower indented portion 6b, while a pair of retainer plates 7 and 8 are respectively provided with protruded portions 7a and 8a coupled with the protruded and indented portions 6a and 6b of the leaf spring 5. Thus, the leaf spring 5 is accurately positioned and retained in place by means of the retainer plates 7 and 8 coupled thereto. It has, however, been observed that as is illustrated in FIG. 10(b), there occur cracks 6c along the reinforcement fibrous sheet-like materials in the upper protruded portion 6a of leaf spring 5, resulting in decrease of durability of the leaf spring 5.